Methods and chemical solutions for cleaning photomasks using quaternary ammonium hydroxides

Abstract

Embodiments provided herein describe methods and chemical solutions for cleaning photomasks. A photomask is provided. The photomask is exposed to a chemical solution. The chemical solution includes a quaternary ammonium hydroxide. The quaternary ammonium hydroxide may include at least one of tetraethyl ammonium hydroxide (TEAH), tetrapropyl ammonium hydroxide (TPAH), or a combination thereof. The photomask may be an extreme ultraviolet (EUV) lithography photomask.

What is claimed: 
     
         1 . A method comprising:
 providing a photomask; and   exposing the photomask to a chemical solution, wherein the chemical solution comprises a quaternary ammonium hydroxide.   
     
     
         2 . The method of  claim 1 , wherein the photomask is an extreme ultraviolet (EUV) lithography photomask. 
     
     
         3 . The method of  claim 2 , wherein the quaternary ammonium hydroxide comprises at least one of tetraethyl ammonium hydroxide (TEAH), tetrapropyl ammonium hydroxide (TPAH), or a combination thereof. 
     
     
         4 . The method of  claim 3 , wherein the photomask comprises ruthenium. 
     
     
         5 . The method of  claim 4 , wherein the photomask further comprises tantalum, molybdenum, and silicon. 
     
     
         6 . The method of  claim 5 , wherein the chemical solution further comprises a surfactant, wherein the surfactant comprises at least one of t-octylphenoxypolyethoxyethanol, trimethylnonylpolyethylene glycol, or a combination thereof. 
     
     
         7 . The method of  claim 6 , wherein the chemical solution further comprises at least one of diethylenetriamine (DETA), n-methyl-2-pyrrolidone (NMP), or a combination thereof. 
     
     
         8 . The method of  claim 7 , wherein the chemical solution comprises about 15 mass % TEAH, about 1 mass % t-octylphenoxypolyethoxyethanol, and about 0.1 mass % DETA. 
     
     
         9 . The method of  claim 8 , wherein the chemical solution is heated to about 80° C. when the photomask is exposed to the chemical solution. 
     
     
         10 . The method of  claim 7 , wherein the chemical solution comprises about 10 mass % TPAH, about 1 mass % t-octylphenoxypolyethoxyethanol, and about 0.1 mass % DETA. 
     
     
         11 . A method for cleaning a photomask, the method comprising:
 providing a photomask, wherein the photomask comprises ruthenium, tantalum, molybdenum, and silicon; and   exposing the photomask to a cleaning solution, wherein the cleaning solution comprises a quaternary ammonium hydroxide and a surfactant.   
     
     
         12 . The method of  claim 11 , wherein the quaternary ammonium hydroxide comprises at least one of tetraethyl ammonium hydroxide (TEAH), tetrapropyl ammonium hydroxide (TPAH), or a combination thereof. 
     
     
         13 . The method of  claim 12 , wherein the surfactant comprises at least one of t-octylphenoxypolyethoxyethanol, trimethylnonylpolyethylene glycol, or a combination thereof. 
     
     
         14 . The method of  claim 13 , wherein the cleaning solution further comprises at least one of diethylenetriamine (DETA), n-methyl-2-pyrrolidone (NMP), or a combination thereof. 
     
     
         15 . The method of  claim 13 , wherein the photomask comprises:
 a substrate;   a multi-layer stack formed above the substrate, wherein the multi-layer stack comprises a plurality of alternating first and second layers, the first layers comprising molybdenum and the second layers comprising silicon;   a capping layer formed above the multi-layer stack, wherein the capping layer comprises ruthenium; and   an absorber layer formed above the capping layer, wherein the absorber layer comprises tantalum.   
     
     
         16 . A chemical solution for cleaning an extreme ultraviolet (EUV) lithography photomask comprising ruthenium, wherein the solution comprises:
 a quaternary ammonium hydroxide;   a surfactant;   at least one of diethylenetriamine (DETA), n-methyl-2-pyrrolidone (NMP), or a combination thereof; and   water.   
     
     
         17 . The chemical solution of  claim 16 , wherein the chemical solutions comprises not more than about 20 mass % of the quaternary ammonium hydroxide, not more than about 5 mass % of the surfactant, and not more than about 20 mass % of the at least one of DETA, NMP, or a combination thereof. 
     
     
         18 . The chemical solution of  claim 17 , wherein the quaternary ammonium hydroxide comprises at least one of tetraethyl ammonium hydroxide (TEAH), tetrapropyl ammonium hydroxide (TPAH), or a combination thereof, and the surfactant consists of at least one of t-octylphenoxypolyethoxyethanol, trimethylnonylpolyethylene glycol, or a combination thereof. 
     
     
         19 . The chemical solution of  claim 18 , wherein the chemical solution comprises about 15 mass % TEAH, about 0.1 mass % t-octylphenoxypolyethoxyethanol, about 0.1 mass % DETA, and water. 
     
     
         20 . The chemical solution of  claim 18 , wherein the chemical solution comprises about 7 mass % TPAH, about 0.1 mass % t-octylphenoxypolyethoxyethanol, about 0.1 mass % by DETA, and water.